Electromagnetic overcurrent trip device



Sept 17, 1968 E. H. FREDRICKSQN ETAI.v 3,402,377

ELECTROMAGNETIC OVERCURRENT TRIP DEVICE Filed March 30, 1967 5 Sheets-Sheet l Sept. 17, 1968 E H, FREDRICKSON ETAL 3,402,377

ELECTROMAGNETC OVERCURRENT TRIP DEVICE Filed March 50, 1967 5l Sheets-Sheet 2 Sept. 17,' 1968V E. H. FREDRICKSON ETAL 3,402,377

ELECTROMAGNETIC OVERCURRENT TRIP DEVICE Filed March 3o, 19e? 5 sheets-sheet 5 BY HPA/VK .f fax/@wwf Sept. 17, 1968 Y E. H. FREDRICKSON ETAL ELECTROMAGNETIC OVERCURRENT TRIP DEVICE Filed March 3o, 1967 5 Sheets-Sheet -4 Sept. 1'7, 1968 E. H. FREDRICKSON ETAL 3,402,377

ELECTROMAGNETIC OVERCURRENT TRP DEVICE Filed March SO, 1967 .Y 5 Sheets-Sheet 5 United States Patent O 3,402,377 ELECTROMAGNETIC OVERCURREN'I` TRIP DEVICE Einar H. Fredrickson, Ambler, and Frank J. Pokorny,

Hatboro, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Mar. 30, 1967, Ser. No. 627,095 26 Claims. (Cl. 335-240) ABSTRACT F THE DISCLOSURE A trip device for a circuit breaker including an electromagnet and an armature which is rotated to trip the circuit breaker in response to predetermined magnitudes of current flowing through the electromagnet. The armature is pivotally rotatable about a bushing upon which bushing also rotates a rocker arm. One end of the rocker arm is linked to a time delay element, while the other end of the rocker is connected to the armature in such a manner as to rigidly connect the two during normal operation while at the same time permit variation in the angular separation therebetween to permit variation of the delay introduced by the time delay element. Additionally, an anti-rattle spring arrangement is provided which also extends the operating life of the device.

This invention relates to overcurrent trip devices and current trip device of utmost simplicity, comprising parts of the most economical nature, and capable of maintaining consistent time and current calibrations over extended periods of use.

As well known in the art, circuit breakers are useful to rapidly disconnect loads from lines which may be subject to overload conditions beyond a predetermined maximum time limit and/or instantaneous short circuit conditions. Generally speaking, circuit breakers include some type of overcurrent trip device which monitors the current fiowing in the line within which the circuit breaker has been inserted,

A typical overcurrent trip device of the prior art, and in fact the type of trip device in which the instant invention may find application, is an electromagnetic trip device, so designated because of its manner of detecting the various fault conditions iiowing in the line, Specifically, the line current entering the trip device flows through a conductive loop which surrounds the core of a magnet. An associated armature is normally biased away from the magnet. Upon the occurrence of predetermined magnitudes of current flowing through the line, and hence through the coil of the thus defined electromagnet; the armature is drawn into engagement with the magnet such that a portion of the armature strikes the tripper bar of the circuit breaker whereby, and as will be understood by those skilled in the art, the stored energy system of the circuit breaker is released to initiate an opening ofthe circuit breaker contacts to disconnect the load being protected from the line.

To add desired time characteristics to the movement of armature, various modifications of the basic trip device are possible. For example, the armature may be linked to the piston of a duid-filled dashpot which, as will be further explained, introduces a predetermined time delay between the occurrence of the current fault suflicient to attract the armature and the time such ar'mature actually reaches its engaged position to trip the breaker. Additionally, a second armature may be provided to trip the breaker in the event of short circuit conditions and might be restrained only by a mechanical timer of short duration.

3,402,377 Patented Sept. 17, 1968 The instant invention is in fact directed to an electromagnetic overcurrent trip device of the type discussed above, and includes, in its preferred embodiment, a duid-filled dashpot connected in a novel manner to the associated armature. Generally speaking, and as will be further explained in greater detail, the novel arrangement for interconnecting the piston of the fluid-filled dashpot and the armature includes a single axis upon which is rotatable the armature and a rocker arm. One end of the rocker arm is linked to the piston of the fiuidafilled dashpot while the other end is adjustably connected to the armature, there being provided adjustment means intermediate the second end of the rocker arm and the armature to separatingly urge these elements apart into tight engagement with one another. As will be seen, the adjustment means perform a dual function in that it rigidly connects the rocker arm to the armature during normal operation of the trip device while, at the same time, it permits variation between the rocker arm and the armature to effect changes in the time delay introduced by the dashpot.

In an alternative embodiment of the instant invention, the interconnection of the fluid-filled dashpot and the armature associated therewith is varied slightly such that the same armature which previously was usable as a long time delay armature now functions in an instantaneous mode to initiate circuit breaker operation upon the 0ccurrence of short circuit conditions.

As a particularly advantageous `feature of the instant invention means are provided to establish essentially rattle-free, and therefore reduced noise operation of the device, and at the same time extend the operating life thereof.

As another embodiment of the instant invention, and as will be further described in detail, the invention provides that a second short time armature, pivoted on the same axis as the rocker arm and first armature, may be added to the trip device to expand the operating characteristics thereof.

Accordingly, it is an object of the instant invention to provide an overcurrent trip device of utmost simplicity, comprising parts of the most economical nature, and capable of maintaining consistent time and current calibrations over long periods of use.

Another object of the instant invention is to provide an overcurrent trip device including an electromagnet; an armature normally biased in a first direction toward a first position away from the electromagnet and rotatable about an axis in a second direction toward a second position in engagement with the electromagnet in response to predetermined overload currents ilowing through the electromagnet; a time delay unit Vfor introducing a preselected amount of time delay between the occurrence of a predetermined current flow and the movement of the armature toward its second position; a rocker arm rotatable about said axis, with a rst end of the rocker arm being linked to the time -delay unit; and adjustment means linked between the armature and a second end of the rocker arm for rigidly connecting the rocker arm and the armature when the armature is rotated in its second direction while at the same time permitting angular separation therebetween when so desired.

Still another object of the instant invention is to provide such an electromagnetic overcurrent trip device in which the above described interconnection of the armature and rocker arm may be easily modified to convert between a time delayed and instantaneous mode of operation.

Another object of the instant invention is to provide such an electromagnetic overcurrent trip device which may be easily combined with a second, or short-time,

armature rotatable about the same axis as the first enumerated armature.

Still another object of the instant invention is to provide such an electromagnetic overcurrent trip device wherein virtually all of the rotating parts thereof are rotatable about a single axis thereby materially simplifying construction while at the same time materially reducing the considerable amount of lost motion, high noise level, and wide variations in calibrations which result from the multiplicity of pivot pins utilized in prior art overcurrent trip devices.

It is another object of the instant invention to provide an electromagnetic overcurrent trip device which includes means to establish essentially rattle-free, and therefore reduced noise operation of the device, and at the same time extend the operating life thereof.

Still another object of the instant invention is to provide such an electromagnetic overcurrent trip device wherein the above mentioned single pivoting axis is provided with an anti-rattle spring arrangement which reduces audible noise due to normal load currents by reducing chatter between parts mounted thereon.

Yet another object of the instant invention is to provide a novel connection between the above mentioned rocker arm and its associated armature which permits relative movement therebetween to permit changes in the time delay introduced by a time delay element linked to the rocker arm.

Other objects and a fuller understanding of the instant invention may be had by referring to the following description and drawings, in which:

FIGURE 1 is a side view, partly in section, of the overcurrent trip device of the instant invention, with certain exterior portions thereof removed to reveal the internal portions thereof;

FIGURE 2 is an exploded perspective view of certain elements found in FIGURE 1;

FIGURE 3 is a view taken along the arrows 3-3 of FIGURE 1;

FIGURE 4 is a view taken along the arrows 4 4 of FIGURE 1;

FIGURE 5 is a partial side view of the overcurrent trip device of FIGURE l, but showing an alternative embodiment thereof; and

FIGURE 6 is a partial view taken along the arrows 6-6 of FIGURE 3 illustrating the side opposite from the side of the overcurrent trip device shown in FIGURE l.

Turning to FIGURE 1, there is shown an overcurrent trip device 10 constructed in accordance with the teachings of the instant invention. Although not specilica'lly shown in FIGURE 1, but as well known in the art, it is understood that the overcurrent trip device 10 of the instant invention is actually to be incorporated in a circuit breaker of any desired number of poles, with one of the overcurrent trip devices 10 associated with each pole. It is to be further understood that although the following description pertains to a single overcurrent trip device inserted in a single line of current, in the event of a multipole circuit breaker were under discussion, the description would be the same for each pole thereof.

The conductor 12 carries current from the line being protected through the conductive turns 14 of an electromagnet, (generally designated 16); through a conductive mem-ber 18, and up to a terminal bracket 20. As well understood in the circuit breaker art, a conductive member may be secured to the terminal bracket 2th as, for example, by the aperture 22, which conductive member would lead to the movable contact arm (not shown) of the circuit breaker in which the overcurrent trip device 10 was employed. The circiut path would be completed through the stationary contact (not shown) of the circuit breaker and from the stationary contact out of the circuit breaker. Since the instant invention is in no way related to the particular circuit breaker which might be utilized, a detailed description of such a circuit breaker is not included in the instant specification. For the purpose of understanding the operation of the trip device 10 within the cooperating circuit breaker, it is suicient to note that upon the occurrence of a predetermined overload or short circuit condition within the line 12, the overcurrent trip device 10 will operate, in a manner to be described in greater detail, to initiate circuit breaker interruption operation which will separate the movable contact arm of the circuit breaker from the stationary contact thereof to interrupt the current ilow through the conductor 12 and thereby protect the load which is serviced by the circuit breaker. It may be noted that in the event a plurality of the trip devices 10 are being utilized in combination with a plurality of poles of a multi-pole circuit breaker, means are usually provided to interconnect the movable contact arms of each phase of the breaker such that the occurrence of an overload or fault condition in one phase of the breaker will initiate a? circuit interruption in all phases thereof.

Turning now to a detailed consideration of the overcurrent trip device 10, for ease of identification it may be broadly stated that the trip device 10 of FIGURE 1 includes five main assemblies, namely, the electromagnet 16, the armature assembly 24, the dashpot 26, the rocker arm 28, and an adjustment assembly generally indicated at 30.

As noted previously, the electromagnet 1'6 includes the conductive turns 14 which surround a leg 32 of a generally U-shaped magnetic core member 34. The core 34 may be constructed of a plurality of stacked laminations, or of any other convenient construction. A unitary insulating member 36 includes a sleeve portion 38 which surrounds the leg 32 as well as a generally L-shaped portion 40 which conforms generally to the internal configuration of the U-shaped core 34.

As best seen in FIGURES 2 and 3, the armature assembly 24 actually comprises two armature plates 42 and 44 which, when secured in assembled relationship, as shown in FIGURE 3, sandwich an armature core section 46 therebetween. As will be seen in FIGURES 1, 2 and 3, both armature plates 42 and 44 are provided with apertures 48 and 50, respectively, by means of which the armature plates 42 and 44 may be rotated about a bushing 52 freely `pivoted on a iixed armature pin 54. A pair of anti-rattle springs 56 are each secured at one end to the armature pin 54 and at the opposite end to a pair of stationary side plates 58 (seen only in FIGURE 3) which support the armature pin 54. It will be appreciated that the anti-rattle springs 56 take up all pin and hole clearances between the side plates 58 and the armature pin 54 and in the same direction as the magnetic pull across the air gap between the armature core section 46 and the lower leg of magnet core 34.

It will be seen in FIGURES l and 3 that armature plate 42 includes an integrally depending portion 60. The lower portion 60 of armature plate 42 includes an upstanding tab portion 62 which carries an adjustable air gap screw 64, the head 66 of which stops against a plate 68 to define the maximum counterclockwise movement of the armature assembly 24. A calibration spring 72 is secured between a calibration indicator 74 and a calibration spring support 76 and as will become apparent continually urges the armature assembly 24 in a counterclockwise direction as viewed in FIGURE 1 to maintain the head 66 of the air gap screw 64 in abutment with the plate 68.

The air gap screw 64 is so named because of its relationship to the size of the air gap 70 existing between the magnetic core 34 and the armature assembly 24 when the armature assembly 24 occupies the position shown in solid line in FIGURE 1. That is, by rotating the air gap screw 64, the armature assembly 24 can be incrementally rotated either clockwise or counterclockwise, depending on the direction of rotation of the air gap screw 64, to vary the size of the air gap '70 to a fixed setting so that preselected magnitudes of current flowing through the conductive turns 14 may attract the armature assembly 24 to its engaged or dotted line position shown in FIG- URE l.

The calibration indicator 74 is threadedly mounted on an upright shaft 78 such that by rotating the shaft 78, as by a nut 80, the calibration indicator 74 can be raised or lowered to either increase or decrease the counterclockwise bias of spring 72 on the armature assembly 24 thereby effecting fine calibration of the magnitude of current flowing through the conductive turns 14 necessary to draw the armature assembly 24 into engagement with the magnetic core 34, while at the same time the indicator 74 provides a visual indication thereof.

As best seen in FIGURE 1, armature plate 42 carries an integrally extending extension 82 upon which is threadably and adjustably secured a trip screw 84. When the armature assembly 24 is attracted to the magnetic core 34 in response to overload conditions in the line 12, the trip screw 84 rotates the tripper bar 86 of the circuit breaker (not shown) to initiate contact separation as described previously.

As already noted, the rocker arm 28 is pivoted on the same bushing 52 as the armature plates 42 and 44 and is in fact sandwiched therebetween, as most clearly seen in FIGURE 2. One end 88 of the rocker arm 28 is linked to the fluid-filled dashpot 26, in a manner to be further described, while the opposite end 90 of the rocker arm 28 cooperates with the armature assembly 24, the calibration spring support 76, and the adjustment assembly, generally indicated at 30, in the following manner.

, Specifically, the end 90 of the rocker arm 28 includes a passageway 92 through which an adjusting stud 94 may freely pass. As most clearly seen in FIGURE 2, the adjusting stud 94 includes a flat head portion 96 provided with an aperture 98 therethrough. Head portion 96 is freely rotatable on a pivot pin 99 (only the cross-section of which may be seen in FIGURE 2) which is held at itsl opposite ends in apertures 100 and 102 provided on armature plates 42 and 44, respectively, when such plates are assembled together in their sandwiched relationship with respect to the armature core 46 and the rocker arm 28.

From the fiat head 96 the adjusting stud 94 tapers into an elongated shaft 104 (which passes through the aperture 92 in the rocker arm) to terminate at its opposite extremity in a threaded end portion 106 upon which a lock nut 108 is threadably mounted. In the embodiment of FIGURES 1, 2 and 3, a tubular spacer bushing 110 is concentrically mounted about the stud 94 and abuts the lock nut 108 at one end and the under surface of the rocker arm at its other end.

On the end 90 of the rocker arm 28 and adjacent the passageway 92 is provided a recessed wall 112 within which is seated a spring 114 normally under compression.

As most clearly seen in FIGURE 2, the calibration spring support 76 also rotates about the bushing 52 and includes an inturned extension or plate surface 116 which, as indicated by the phantom lines in FIGURE 2, seats under the lower surfaces 118 and 120 of the armature plates 42 and 44, respectively, but on top of the uppermost spiral 122 of the compression spring 114 such that, and as may be appreciated in FIGURE l, with respect to one another, compression spring 114 urges the rocker arm 28 and the armature assembly 24 in opposite directions. To look at it from a different viewpoint, assuming the rocker arm 28 to be momentarily stationary because of its cooperation with the iiuid-iilled dashpot 26, to be described below, then the compression spring 114 tends to rotate the plate 116 of the calibration spring support 76 and hence the armature assembly 24 in a clockwise direction about the bushing 52.

However, it will be appreciated that the clockwise rotation of armature assembly 24 is restrained by the adjusting stud 94 which is restrained from clockwise rotation by the spacer bushing interposed between the lock nut 108 and the under surface of the end 90 of the rocker arm 28 (recall that rocker arm has been assumed stationary). Thus, for all intensive purposes, the linkage established through the rocker arm 28; the adjusting assembly comprising stud 94, lock nut 108 and bushing 110; calibration spring support 76 and the armature assembly 24 may be thought of as one entirely rigid assembly, at least so far as clockwise rotation about bushing 52 is concerned.

However, and for reasons to become apparent, the adjusting assembly 30 can be easily manipulated to change the angular relationship of the rocker arm 28 and armature assembly 24. Thus by rotating the lock nut 108, say, for example, clockwise in FIGURE l, then because the armature assembly 24 cannot rotate counterclockwise (head 66 abutting plate 68) the spacer bushing 110 and hence the rocker arm 28 must be rotated clockwise about bushing 52 against the bias of compression spring 114. Similarly rotating the lock nut 108 in the opposite direction permits the compression spring 114 to expand and urge the rocker arm 28 in a counterclockwise direction about bushing 52.

It will be appreciated that the compression spring 114 takes up all bushing and hole clearances between the bushing 52, armature plates 42 and A44, and rocker arm 28 by using the fixed distance between pin 99 and spacer bushing 110 as a pivot to spread the rocker arm 28 and the armature 42 apart against the bushing S2.

As will become app-arent after the description of the dashpot operation, such rotation of lock nut 108 to vary the angular separation between the armature and the rocker arm varies the magnitude of time delay which is introduced by the fluid-filled dashpot 26. A calibration indicator 124 is secured to the end 90 of roc-ker arm 28 and rotates therewith. Thus the angular relationship of the rocker arm with respect to the armature (which corresponds to the magnitude of time delay), may be visually observed by comparing the position of the indicator 124 with a scale (not shown) etched or printed on a cover plate 126 of the device.

Turning now to the fluid-lled dashpot 26, as may be seen in FIGURES 1 and 4, the end 88 of the rocker arm 28 pivotally carries a link 128, the opposite end of which is secured to a piston 130 movable within the oil displacement pot 132. Anti-rattle springs are provided to take up any hole clearance involved between the linkage of the rocker arm 28 and the piston 130 while a iiexible accordion-like cover 1'37 is sealed to the rocker arm in any convenient manner at one end 139 thereof, while at the opposite end 140 thereof terminates in a generally O-shaped sealing ring arrangement indicated at 141. A plug 142 permits filling of the dashpot.

As noted, the interior of the pot 132 is filled with an incompressible fluid 134 which resists rapid movement of the piston 130 and thereby, through the rigid assembly of link 128, rocker arm 28 and the adjusting assembly 30, prevents rapid clockwise movement of the armature assembly 24 in the event the current through the conductive turns 14 exceeds the predetermined maximum. Thus the incompressible fluid 134 resisting rapid movement of the piston 130- introduces a time delay between the moment that the armature assembly 24 4begins to move toward its engaged position and the actual time that it does reach its engaged position to trip the circuit breaker.

Although the dashpot 26 per se, forms no part of the instant invention, a somewhat detailed explanation of its operation is necessary to understand the nature of the adjustment capabilities possible by means of the novel interrelationship of the rocker arm and armature assembly established by the instant invention. Specifically,

rent flowing through conductive turns 14. The slowness of the movement of the entire assembly is due to the incompressible nature of the uid` 134 and the fact that it must escape slowly up, around the periphery 144 of the lower land 146 of the piston 130` before it reaches the open space 147 above the lower land 146.

However, it will be noted that beginning with the point 150' of the pot 132 and below, the internal diameter of the pot 132 is significantly greater than the diameter of the lower land 146 of the piston 130. Therefore, once the upper surface 148 of the lower land 146 passes the point 150', all fluid restraint is removed and the uid 134 is free to rapidly pass through apertures 152 of the piston into the open spaces 147 and above. Thus after a predetermined time delay, dependent upon the initial position of the lower land 146 of the piston 130, the rocker arm 218 is free to rotate clockwise at a rapid rate and the armature assembly 24 is similarly free to complete the last portion of its clockwise travel at a rapid rate of speed. It is during this rapid rate of movement of the armature assembly 24 that the trip screw 84 rotates the tripper bar `86 to initiate the Contact separation operation.

Thus it will be apparent that the amount of time delay introduced by the dashpot 26 will be dependent upon the starting position of the lower land 146 of the piston 130; and the `closer that the upper surface 148 of the lower land 146` is to the point 150 which begins the enlarged diameter of the pot 132, the less time delay will be introduced into the movement of armature assembly 24.

At this point it should be apparent how the adjusting assembly 30 functions to vary the time delay introduced by the dashpot. Specifically, as one rotates the lock nut 108, say clockwise, so that it rides up the threaded portion 106 of the adjusting stud 94, the rocker arm 28 will be rotated clockwise against the bias of compression spring 114 thereby lowering the lower land 146 of piston 130 to shorten the time delay. Similarly, rotating the lock nut 108 counterclockwise would permit the compression spring 114 to rotate the rocker arm counterclockwise thereby raising the lower land 146 of the piston 130 and increasing the time delay effectuated by the dashpot assembly 28. Thus it becomes apparent that the coopera tion of the compression spring 114, the adjusting stud 94, the lock nut 108, and the spacer bushing 110 of the adjusting assembly 30 perform a dual function in that they permit a time-band adjustment while at the same time function as a rigid link between the rocker arm 28 and the armature assembly 24 during 'clockwise rotation of the armature assembly 24 caused by overload currents in the conductive turns 14.

It will also be appreciated that because the fluid 134 is incompressible, and therefore rapid movement of the piston 130 is initially prevented, the dashpot 26 effectively holds the armature assembly 24 in the position shown in FIGURE 1 on high short circuit currents flowing through the conductive turns 14.

To provide for circuit breaker tripping in the event of high short circuit conditions, one possible variation of the trip device of FIGURE 1 is to add, what is commonly designated, a short time armature 154 adjacent the long time armature assembly 24, as shown in FIGURE 3. The short time armature 154 is pivotally mounted on the bushing 53 (adjacent the bushing 52) and is rotated against the bias of a spring 73 (FIGURE 6) into er1- gagement with the magnet 34 in response to short cir cuit current conditions in the line being monitored. Preferably the short time armature 154 is restrained; by a mechanical timer 156 of one second or less duration (see FIGURE 6).

The timer 156 includes an -output shaft 158 which is momentarily restrained by suitable means provided within the timer 156. A crank 160 is secured at one end to the output shaft 158 and at the opposite end to a link member 162 by means of a pivoting pin 164. The link 162 is connected to the bottom portion 165 of the short time armature 154 by a loose pivotal connection indicated at 166.

It will be appreciated that the short delay of the short time armature 154 is small compared to the long time delay introduced by the dashpot 26 and that during the entire operation and movement of the short time armature 154 even as restrained by the mechanical timer 156, the incompressibility of the fluid 134 in the dashpot 26 would prevent the long time armature assembly 24 from being attracted to the magnet 34.

Turning to FIGURE 5, there is shown an alternative embodiment 30' of the adjusting assembly 30 of FIG- URE l. In this embodiment thearmature assembly `24 functions in an instantaneous mode of operation for short circuit currents as well as a long time delay mode of operation for overload currents described with respect to FIG- URES 1 and 2. Specifically in FIGURE 5, the spacer bushing of FIGURE l has been replaced by a compression spring 168 an-d a calibration indicator 170 located be. tween a washer 172 and nut 174. The compression spring 114 of FIGURES 1 and 2 is replaced by an adjusting screw 176 which is threaded through a passageway 178 leading into the recess 112 and which bears against the plate-like surface 116 of the calibration spring support 76 (see FIG- URE 2). The adjusting screw 176 is frictionally locked in place by a compression spring 180.

The operation of the embodiment of FIGURE 5 in an instantaneous -mode of operation is as follows. Upon the occurrence of a fault condition in the conductive turns 14 of the electromagnet 16, the armature assembly 24 will be instantly drawn toward the magnet core 34. However, in this embodiment because the rigid spacer bushing 110 of FIGURE 1 has been replaced by the compressible spring 168, upon rotation of the armature assembly 24, the adjusting stud 94 is free to rotate, i.e., be pulled through the aperture 92 against the bias of compression spring 168 while the rocker arm 28 remains stationary because of the incompressible nature of the fluid in dashpot 26. Hence the armature assembly 24 may quickly move to the engaged position causing the tripping of the circuit breaker by the trip screw 84, in a manner discussed previously.

It is to be appreciated that either the instantaneous mode of operation of FIGURE 5 or the time delayed mode of operation of FIGURE 1 may be used in combination with the short time armature embodiment of FIGURE 6, or, in the alternative, either the embodiments of FIGURE l or 5 may be used alone depending upon the requirements of the user. l

As noted previously, an important aspect of the instant invention resides in providing an over-current trip device which is essentially noise-free and which has an extended period of life. A detailed explanation of the manner in which the instant invention makes such operation possible will now be presented.

vReferring to FIGURES 1 and 3, a vibratory assembly 189 consists of a weight 190 mounted on one end of a flexible spring wire 193 whose deflection at high overload currents is limited by the slot 195 in an upstanding tab 197 0n armature plate 42. The other end of the wire 193 is anchored in a cross-hole 199 in a stud 191 having a portion 201 passing through an aperture 203 in armature plate 42 and rigidly mounted in place by a nut 192 threadably mounted thereon.

The vibratory assembly 189 is used to keep the noise level low and extend the operating life of the overcurrent trip device when normal alternating currents equal to or less than the rating of the device flow in conductive turns 14. The vibratory assembly 189 is also a factor in reducing noise and pivot pin wear, thereby increasing the operating life of the trip device, when the currents are substantially above the rating of the device. Specifically, in either case, whenever the increasing portion of an alternating current cycle exceeds the rating of the device, the restraining force of the calibration spring 72 is exceeded and the magnetic pull resulting therefrom attracts the armature 24 toward the core 34. Similarly, as the current within the A.C. cycle decreases to zero, the magnetic pull will reach a point where the calibration spring 72 is stronger than the magnetic pull and the armature 24 will attempt to return to its initial position. This vibratory movement is infinitestimally small, but is repeated for every half cycle of current flowing in conductive turns 14.

That portion of the magnetic pull described above which overrides the restraining calibration spring pull represents pulses of kinetic energy which imparts motion to the vibrator weght 190 causing it to deflect against the spring effect of spring wire 193. When the remaining portion of the magnetic pull is less than the calibration spring pull (as the current in the A.C. cycle approaches Zero), the vibrator Weight can now give up its stored energy to the armature. It has been found that when all these -forces are added vectorily, the resultant force on the armature is pulsating, but is in the same counterclockwise direction as the calibration spring 72. This tends to hold armature 24 against the stop plate 68 without vibration. Thus, the vibrator assembly 189 alternately absorbs and gives up kinetic energy in an intermittent relationship in respect to the inlinitestimally small vibrations of the armature which accompany alternating current operation, thereby effectively smoothing out operation during both normal A.C. current ow and A.C. current fiow above the rating of the device. It will be appreciated that all parts of the overcurrent trip device wear significantly better in such en vironment and simultaneously the noise level is reduced.

It should be emphasized that the above description of the operation of the vibrator assembly 189 pertains to ideal or theoretical vibration action for a trip device in which there is zero clearance between all pins and their cooperating holes such as, for example, the pins and holes joining the end 88 of the rocker arm 28 to the piston 130 of the dash-dot assembly 26; and the pin 54 and surrounding bushings 52, 53 supported within the apertures in plates 58 upon which bushings are supporting the rocker arm 28, calibration spring 76 and armature assemblies 24 and 154. To further appreciate the manner in which the instant invention further reduces noise and extends the operating life of the device, the `vibratory action described above must be considered in the environment of freely fitting pins having the usual production line clearances within their cooperating apertures.

When the pulses of magnetic pull overriding the calibration spring 72 appear at the armature 24, they now see an increment of free motion for all parts back to the piston 130, which increment of free motion is equal to the sum of the clearances at each pivot pin. This might be analogized to pulling taut a loose chain until all the links are tight. Under these conditions, each pin in the chain initially receives a high instantaneous take-up force, and when the calibration spring 72 once again overrides the magnetic pull (as the A.C. cycle passes through zero), all the parts l become loose again. Since this action takes place for every half cycle of A C. current, this process produces chatter, accelerates pin wear, and eventually decreases the operating life of the trip device.

With the instant invention, the instantaneous take-up and reduction of clearance is initially reduced by the fact that in the instant device only three pins are used in the entire system between the armature assembly 24 and the piston 130. One such pin and cooperating hole combination includes the pin 211 by which the end 88 of the rocker arm 28 is connected to the link 128. However, and as noted previously, two springs 135 are anchored at one end to the plate 138 (which is screwed to the piston 130) and anchored at the other end, to the pin 211. Thus, springs 135 take up all pin and hole clearances on one of the aforementioned three pin-s and eliminates possible vibration therefrom.

The second pin and hole combination may be thought of as generating clearances between the bushing 52 and 10 the center hole 213 of the rocker arm 28 and the holes 48, 50 in the armature plates 42 and 44. However, and as noted previously, compression spring 114 takes up all clearances between the bushing 52 and the holes in the armature plates and rocker arm. Thus, the clearances and consequent chatter in the second pin and hole combination have been eliminated. Similarly, anti-rattle springs 56 take up clearance between pin 54 and the holes in plates 58.

The one pin and hole combination not yet accounted for is the pin 54 within the Ibushing 52 generating clearance therebetween. However, to eliminate vibration at this point, the parts are intentionally manufactured very large to reduce the bearing stress to a low value and thereby eliminate chatter.

Now it becomes apparent that when the pulses of magnetic pull which override the calibration spring 72 appear at the armature 24, they see one entire rigid assembly all the way from the armature assembly 24 to the `dashpot assembly 26 and the theoretical vibratory action described previously effectively becomes a reality.

As shown in FIGURES 2 and 6 a second vibratory assembly 189a is secured to the short time armature 154 in the same manner as assembly 189 is secured to armature assembly 24. Operation and function thereof is similar to the description given for assembly 189 and need not be repeated.

It may -be noted that devices in accordance with the instant invention have been successfully tested at current levels of three times normal rating for three million pulses of two seconds duration. This is to ybe compared to previous devices not incorporating the rattleafree construction of the instant invention, which prior devices rbarely passed fifty thousand such pulses. Thus, the instant invention makes possible a life expectancy at least sixty times prior art devices.

Thus there has been described an electromagnetic overcurrent trip' device which establishes a novel rigid, but adjustable interconnection between a uid-filled dashpot and the cooperating armature assembly of the trip device. It is to be appreciated that the simplicity of the arrangement described herein permits the user to easily lmodify the trip device to permit a single armature assembly to function either in a time delayed or instantaneous mode of operation, and that either of such modes of operation may be simply combined with a short time armature restrained, in the preferred embodiment, by a single mechanical timer. It is to be further appreciated that the provision that all rotatable parts of the overcurrent trip device be rotatable about a single common bushing materially reduces the number of movable parts and pivot pins present in the device and therefore inherently increases the life expectancy thereof while at the same time materially reducing undesirable noise or chatter during the operation of the device.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. For instance, it is possible that the adjusting stud 94, in the embodiment of FIGURE l, might be rigidly secured to the `rocker arm 28 and movable with respect to the armature assembly 24. That is, reversed, while performing the exact same function. Therefore, this invention is to be limited, not by the specific disclosure herein, but only -by the appending claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. An overcurrent trip device comprising:

an electromagnet;

first armature means normally biased in a first direction toward a first position and rotatable about an axis in a second direction toward a second position in response to predetermined current fiow through said electromagnet;

first time delay means for introducing a preselected amount of time delay between the occurrence of said predetermined current fiow and the movement of said first armature means toward its second position;

a rocker arm rotatable about said axis, a first end of.'

said rocker arm being linked to sai-d first time de-v lay means; and

adjustment means linked `between said first armature means and a second end of said rocker arm for rigidly connecting said rocker arm and first armature means when said first armature means is rotated in said second direction while at the same time permitting angular variation between said first armature means and said second end of said rocker arm.

2. The overcurrent trip device of claim 1, wherein said adjustment means includes normally compressed biasing means interposed between said second end of said rocker arm and said first armature means.

3. The overcurrent trip device of claim 1, wherein said first time Idelay means includes an element prohibitively movable between a preselected first and second position, said preselected amount of time delay being dependent upon the locations of said preselected first and second positions of said element, and wherein angular variation between said first armature means and said second end of said rocker arm causes said first end of -said rocker arm to vary said first and second position of said element.

4. The overcurrent trip device of claim 3, wherein said first time delay means is a fiuid-filled dashpot and said element is a piston prohibitively movable therein, said first end of said rocker arm being linked t said piston.

5. The overcurrent trip device of claim 4, and further including:

second armature means normally biased toward a first position and rotatable about said axis toward a second position in response to predetermined short circuit current flow through said electromagnet.

6. The overcurrent trip device of claim 5, wherein said dashpot is filled with generally incompressible fiuid which is slowly displaced by said piston as it moves between its first and second position, said incompressible fiuid preventing a rapid movement of said piston from its first toward its second position such that only said second armature means can be moved toward its second position in response to said predetermined short circuit current fiow through said electromagnet.

7. The overcurrent trip device of claim 4, wherein said dashpot includes a flexible cover portion which prevents the fiuid of said dashpot from escaping therefrom, said flexible cover being secured at one end to said dashpot and at the other end to said rocker arm such that the joint between said rocker arm and said piston is encompassed thereby.

8. The overcurrent trip device of claim 3, wherein said adjustment means includes:

biasing means interposed between said first armature means and said rocker arm for urging them in opposite directions; an adjusting stud secured at one end thereof to said first armature means and freely movable with respect to said rocker arm at a second end thereof; and

selectively positionable locking means cooperating with said rocker arm and said second end of said adjustment stud for rigidly connecting said rocker arm to said first armature means at a predetermined angular separation.

9. The overcurrent trip device of claim 8, wherein said rocker arm includes a passageway through which said second end of said adjusting stud passes, and said selectively positionable locking means includes a lock nut threadably engaging said second end of said adjusting stud and a spacer bushing concentrically mounted about said second end of said adjusting stud and spaced intermediate said lock nut and said rocker arm.

10. The overcurrent trip device of claim 1, wherein said axis is defined by a lcommon bushing assembly the ends of which are supported by a pair of spaced apart plates, and further including a pair of springs each connected between one of the ends of said common bushing assembly and one of said plates to provide an anti-rattle arrangement therebetween.

11. An overcurrent trip device comprising:

an electromagnet;

first armature means normally biased in a first direction toward a first position and rotatable about an axis in a second direction toward a second position in response to current fiows of varying predetermined magnitudes through said electromagnet;

first time delay means for introducing a preselected amount of time delay between the occurrence of a first magnitude of current flow and the movement of said first armature means toward its second position;

a rocker arm rotatable about said axis, a first end of said rocker arm being linked to said first time delay means; and

linking means connected between said first armature means and said rocker arm for permitting said first armature means to rotate in its second direction independent of said rocker arm upon the occurrence of a second magnitude of current fiow higher than said first magnitude of said current flow.

12. The overcurrent trip device of claim 11, wherein said first time delay means includes an element prohibitively movable between a preselected first and second position for introducing said predetermined amount of time delay, but prevented from moving from its first toward its second position at a high rate of speed in response to predetermined high fault currents flowing through said electromagnet.

13. The overcurrent trip device of claim 12, wherein said linking means includes compressible spring means normally urging said first armature means and rocker arm toward one another and wherein the force of said compressible spring means is overcome by force developed by said electromagnet in response to said predetermined high fault currents fiowing therethrough, such that said first armature means rotates in its second direction to its second position against the bias of said compressible spring means, while said element of said first time delay means and consequently said rocker arm are prohibited from moving in response to said predetermined high fault currents.

14. The overcurrent trip device of claim 12, wherein said first time delay means is a fiuid-filled dashpot and said element is a piston prohibitively movable therein, said first end of said rocker arm being linked to said piston, said dashpot being filled with generally incompressible fiuid which is slowly displaced by said piston as it moves between its first and second position, said incompressible fiuid preventing a rapid movement of said piston from its first toward its second position.

1S. The overcurrent trip device of claim 14, wherein said linking means includes:

a stud secured at one end to said first armature means and at its other end passing through said rocker arm, said stud having a stop nut thereon;

compressible spring means disposed about said stud between said stop nut and said rocker arm;

whereby the force of said compressible spring means is overcome by force developed by said electromagnet in response tosaid predetermined high fault currents fiowing therethrough, such `that said first armature means rotates to its second position against the bias of said compressible spring means, while said piston and consequently said rocker arm are prohibited from moving in response to said predetermined high fault currents.

16. The overcurrent trip device of claim 11, wherein said axis is defined by two bushings and a pin, the ends of which pin are supported by a pair of spaced apart plates, and further including a pair of springs each connected between one of the end of said pin and one of said plates to provide an anti-rattle arrangement.

17. An overcurrent trip device comprising:

an electromagnet;

a long time armature normally biased toward a first position and rotatable about an axis toward a second position in response to predetermined current flow through said electromagnet;

a uid-filled dashpot including a piston prohibitively movable between first and second positions by incompressible fluid which is permitted to be slowly displaced by said piston during its movement, said fluid preventing rapid movement of said piston from its first toward its second position;

a rocker arm rotatable about said axis, a first end of said rocker arm being linked to said piston;

biasing means interposed between said rocker arm and said long time armature for urging said rocker arm and long time armature apart;

adjustable fastening means cooperating with said rocker arm and long time armature for joining a second end of said rocker arm and said long time armature together against the bias of said biasing means;

a short time armature normally biased toward a first position and rotatable about said axis toward a second position in response to predetermined fault current flow through said electromagnet; and

short time delay means inhibiting the movement of said short time armature between its first and second po- 'sition;

whereby upon the occurren-ce of said predetermined overload current, said fluid will inhibit the movement of said piston between its first and second position to delay movement of said rocker arm and consequently said long time armature toward its second position; and upon the occurrence of said predetermined fault current said fluid will prevent rapid movement of said piston such that said rocker arm and long time armature will be prohibited from moving while said short time armature will be free to move to its second position under the influence of said short time delay means.

18. An overcurrent trip device comprising:

an electromagnet;

an armature normally biased toward a first position and rotatable about an axis toward a second position in response to predetermined current flow through said electromagnet;

a uid-filled dashpot including a piston prohibitively movable between first and second positions by incompressible fluid which is permitted to be slowly displaced by said piston during its movement, said fluid preventing rapid movement of said piston from its first toward its second position;

a rocker arm rotatable about said axis, a first end of said rocker arm being linked to said piston;

compressible spring means coacting between said rocker arm and armature for urging said rocker arm and armature toward one another; and

adjusting means coacting between said rocker arm and said armature for selectively urging said rocker arm and armature apart to establish a firm connection therebetween;

whereby upon the occurrence of a predetermined overload current said uid will inhibit the movement of said piston between its first and second position to delay movement of said rocker arm and consequently said armature toward its second position; and upon the occurrence of a predetermined fault current said fluid will prevent rapid movement of said piston such that said rocker arm will be prohibited from moving but said compressible spring means will be compressed to permit said armature to rotate to its second position while said rocker arm remains stationary.

19. The overcurrent trip device of claim 1 and further including vibratory means connected to said first armature means for intermittently absorbing and dissipating hermetic energy in response to vibrations of said first armature means.

20. The overcurrent trip device of claim 19 wherein said vibratory means includes a weight secured to one end of a spring wire; the opposite end of which is fixedly secured to said first armature means.

21. The overcurrent trip device of claim 19 wherein said first end of said rocker arm and said first time delay means are linking by anti-rattle spring means.

22. The overcurrent trip device of claim 11 and further including vibratory means connected to said first armature means for intermittently absorbing and dissipating hermetic energy in response to vibrations of said first armature means.

23. The overcurrent trip device of claim 22 wherein said first vibratory means includes a weight secured to one end of a spring wire; the opposite end of which is fixedly secured to said first armature means.

24. The overcurrent trip device of claim 22 wherein said first end of said rocker arm and said first time delay means are linking by anti-rattle spring means.

25. The overcurrent trip device of claim 5 and further including vibratory means connected to said second armature means for intermittently absorbing and dissipating hermetic energy in response to vibrations of said second armature means.

26, The overcurrent trip device of claim 25 wherein said vibratory means includes a weight secured to one end of a spring wire; the opposite end of which is fixedly secured to said second armature means.

References Cited UNITED STATES PATENTS '2,060,492 ll/ 1936 Dyer 335-239 2,486,596 11/1949 Graves 335-239 2,632,823 3/1953 Oppel 335-62 BERNARD A. GILHEANY, Primary Examiner.

H. BROOME, Assistant Examiner. 

